models.py

"""
https://groups.google.com/forum/#!topic/django-oscar/BMibGnLb6w0

I've replaced the Partner model. AbstractPartner already carries a ManyToMany field to users (which is not used as far as I can tell). My model instead got a OneToOne field to users and duck-typing to ensure compatibility with Oscar. https://gist.github.com/4690160 
I create a Partner instance for every User via a post_save signal.
When a Product with StockRecord is created, Stockrecord.partner gets set to self.request.user.partner, and hence the connection is made.

The dirty work is overriding all the get_query_set functions in dashboard views to limit results to the logged in user. An example:

# views.py
class FilteredProductListView(ProductListView):

    def get_queryset(self):
        qs = super(FilteredProductListView, self).get_queryset()
        partner = self.request.user.partner
        return qs.filter(stockrecord__partner=partner)

So far, I haven't run into any issues with my solution.
"""
class Partner(models.Model):
    """
    New partner class.

    Note: 'name' and 'users' are dropped from Oscar's partner model.
    """
    user = models.OneToOneField('auth.User')

    def __unicode__(self):
        return u'%s: %s' % (_('Fulfillment Partner'),
                            self.user)

    @property
    def name(self):
        """
        Duck-typing to not break Oscar.
        """
        return unicode(self)

    @property
    def users(self):
        """
        Duck-typing to not break Oscar.
        """
        return [self.user,]

    class Meta(AbstractPartner.Meta):
        pass